The aim of this program is to develop and bring to commercialization a new ultrasound Doppler device to be used to monitor the flow in dialysis access grafts. By detecting falling flow before the graft thromboses, this instrument can significantly reduce the $1 billion and thousands of days of hospitalization now caused by these graft failures. In a small group of dialysis patients, a research version of this device has been shown to be accurate while quickly measuring graft flow, and, because of its unique automatic operation, has been used by non- specialists. Because of its low cost, ease-of-use, and speed, weekly measurements of graft flow are practical, rather than the monthly intervals that other systems have required. Additionally, because the ultrasound Doppler instrument is used before the patient is connected to the dialysis machine, it is not affected by the hemodynamic changes caused by hemodialysis, nor does it interrupt the dialysis procedure, unlike other systems that have been used up to now. In this Fast Track Proposal, Phase I will validate the instrument's sensitivity and specificity in a statistically significant sized group, and test the operator-independence of the measurement. If the instrument meets the goals set in Phase I, Phase II will establish a randomized, controlled clinical trial, comparing a control group having usual care with a matched experimental group being monitored weekly with the new device. Total medical costs and hospitalization associated with the two groups will be captured and compared, with the hypothesis being tested that the monitored group will show significantly reduced access-related costs and improved quality of life, as measured by hospitalization. During Phase I and II, the research instrument will be redesigned as a small, portable unit with a PDA as the interface to the user. Production prototypes will be ready by the end of Phase II so that commercialization will be able to proceed quickly.